Fast rising sounding balloon



Dec. 27, 1949 L. w. lsoM FAST RISING SOUNDING BALLOON Filed Aug. 16,1948 INVENTOR. Langley W lsom Patented Dec. 27, 1949 o-N iiz so: szrnrE's FAST-RISINGSOUNDINGBALLO'GN Eangley' W; Isom; Belmont} Mass,assign'or w Dewey anfli Alm'y Chemical Company, North Gambridge;-.-Massa. a. corporation of- Massaw chusetts:

ApplicatiorfAugust' 16, 1948, Serial Nb".- 44,512

shape of the balloom As such" a-- balloon rises there is a relative'-wind" velocity acting againstthe top -o-i the-balloon.- Thisvelooityheadtends to flatten the balloon;- causing the horizontal-di ameter toincrease and the vertical diameter to decrease, resulting-man ob'latespheroid balloon;

Unfortunately; the balloon do'esnot even maintain this deformed shape;but; because of internal restoring forces and the resultingdecreasedvelocity, springs back approachingitsoriginal spherical form.The net-result is an'oscill'ation' between an oblate spheroid and-a nearspherical form.

This oscillation can be overcome and the ascension rate can be increasedif'suflicient pres 2 of the envelopes; tendtto be spherical. It: isdifli tcult to: avoid this shape limitation. On the other hand.a-non-elastic-balloonLcantbe maderinishapes' deviating widely from:spherical. such'alba'lloon can be made. streamlined and. thus have: a:still higher ascension velocity.

It is. the 1 obj ectiof. my: invention .to: produce: a non-elasticballoon that. maintains: at constant: liitin'g -force, .ascends atia.constantvelocity; .vents no gas; and. isatiall:.timessfillediandrrigida My invention Willi become evidentfromthe r drawings. Figure:- 1:- shows a verticali'section. off theballoon with means for? accomplishingthe above objectsr Figare'=:2- sapartialiverticalsece tion of another: featurei off' this invention.

The balloon consistsof" an =elastici. envelopes if havinga neck |a.-This envelope lislcomplete ly: surrounded by a2. light weightnon-elastic fabricenvelope 2 so: constructedas to: be elonesure can bemaintained within-the balloon to gated vertically and widerr at? the topthan. at

keep it tight and'rigid'. The=pressure cannotbe increased in an elastioballoon;- Introduction of more gas causes such abalfo'on-to expand? thepressure remains constant. Tomaintain sufiithe bottom to give theballoon' when :filledLWith': gas a streamlined shape; In the necks: Ia;and, 2a of these' envelopes: l' and: 2: is at: light; non-- porous 1plug" 4' having a cylindrical: aperture: la

oient pressure withinaballoontolieep it rig-id throughthe center, and.another: smaller: oylin-- requires the envelope to'be non-elastic; Heretofore the usual practice w-ith' non elastic bal loons has been tofill-'- the balloon with' thed'- sired gas, helium orhyd-rogen', andthen" provide-r means for allowingthe gas to escape. as the-:

relative internal pressure increases during the"- ascension of theballoon. If this -werenot -d0ne the envelope would soon burstiiom theincreasedinternal relative pressure. Allowingthe escap'e" of gas in thismanner" causes the ascension ve=-- locity to. decrease: during thaascension until sufiicient gas escapesi for the net lifting force: to'be zero, when itilevels oii and maintains a:- constanti altitude. Thiseffect is undesirable in sounding balloons whichia-re used-ltorcarryin'e40 struments to the desiredialtitudesiand then burst-l torelease theinstruments; It: isidesirable -that such a balloon; especially'whenucarryinga ra'dio-- sonde, rise at a constant: velocity.untilcitiburstss.

Allowing gas. to: escape; inithis: mamrer'is'. also: 8.5.

waste. of gas: Sufiicient: gas to; provide r the dot sired buoyancyattthe; propels altitude is: all .:that:'- need. be used.Thistamount-.of.tgas:.would filllthe balloon at the proper altitude; butnot: at. sea. level where the pressureiis' greater; the: gas isusedmerely torfi-llthe/balloon atlseaa. level.

Another advantage. ofi: a: non-elastic; balloon; over anelastic-balloontis thatgreaterzfreedompfs.

The. rest of drical apertureiib' throughianotherrpart of the: plug 4.The? necks la; and; 2m of. the: envelopes-1 I- and!are:secured;-toifthe;plug.e by seizing 'Ihroug-h'- the larger central?aperture 4a of the: plug 4is-insertedithenentrance-ztube iia ofa con.--stant differential pressure: valve-6, the: outlet of" which vents: tothe. atmosphere; This, valve; 5 consists simply of. the: tube: fi'wwhichis closed. by an adjustable springiloadedzidiaphragm. Inside of; the!envelopes l and: Zzis an' elastic en-- velope having. azneck. 3a.: The:neck; 3a: com. municates. 170: the: constant differential pressure valve6.. by inserting the rentrancevtube 6a of: the valve 6 into the neck;fiarandrsecuring the neck- 3a. around-the 'tuberfim bygseizing" 1-. lnthe same: manner that; the: necks laaa'nd .2aof. the. enve--- lopes land mare-secured 1 to t the. plug. 4-:

I.- have'. found" a finenessi ratio- (theratio of height to greatestwidth), of: about 2:1 t0 be'the--- most satisfactory. Balloonswithratios substan tiallyj'lower than this areiless streamlined resulting ina sacrificeof ascensionvelocity. Increasing; the fineness ratio: of.the. balloon substanitally" above 2:1 increases the ratio; ofsurfacearea to volumeresultlng lnlarger and heavier envelopes whi'chare notwarranted:- by any sub-- stantial increase in ascension velocity.

To increase.- the-stability of the. balloon during. its ascension ithassbeer'r.v found. desirable. to proshape Elastic: ballbons,.becauseeof the naturexz-videthree'or:'fourfins -l=l?llwnear therlOWElTEHd of theballoon. These fins II-II consist of approximately triangular pieces ofa strong fabric as balloon cloth symmetrically placed near the tail ofthe balloon in vertical axial planes. The fins IIII are secured to thefabric envelope 2 and are held distended by radial bowed spring strutrods II0 the ends of which rods fit into pockets II 'z-I Ia provided atthe outermost corners of the fins II-I I. The inner ends of the strutrods I0I0 are secured to the lower side of the end plug 4. A moredetailed description of the fins II-II and struts I0-I0 assembly isgiven in United States Letters Patent, Number 2,398,744.

The envelopes are filled with gas through the tubes 8 and 9. Tube 8passes through the smaller aperture db in plug 4 and communicates withthe interior of the envelope I, and is secured tightly to the inner wallof the smaller aperture 41) in plug 6 to prevent the leakage of gas. Thetube 8 is conveniently closed by the tapered plug 8a. Tube 9 enters theentrance tube 6a of the valve 6 and is in communication with theinterior of the envelope 3 through the entrance tube 6a of valve 6. Tube9 is conveniently closed by the tapered plug 0a.

In operation the envelope I is inflated by connecting the open end oftube 8 to a hose which leads to a source of gas, as hydrogen or helium.Sufficient gas is introduced to the interior of envelope I to impart tothe balloon the desired lifting force. This can be done conveniently bytemporarily securing to the balloon a weight equal to the desiredlifting force and allowing gas to enter the envelope I through the tube8 until the balloon will just lift this weight from the ground. Tube 8is then closed with the stop-per 8a, and the weight is removed. Theconstant differential pressure valve 6 is then adjusted to allow theescape of air from the interior of the envelope 3 when the pressurewithin the envelope I increases beyond the amount sufiicient to hold theenvelope I and its surrounding envelope 2 completely distended. Air isthen introduced through the tube 9 into the envelope 3 in similar manneruntil the envelope 3 has expanded sufficiently to raise the pressure inthe envelope I to the desired amount at which point the differentialpressure relief valve 6 opens prohibiting the entrance of more air intothe envelope 3. At this point the tube 9 is closed by the plug 9a.

The pressure in envelope 3 is determined solely by the pressure inenvelope I and is always higher than the pressure in envelope I by aconstant and very slight amount. By maintaining a constant pressurerelative to the atmospheric pressure within the envelope 3 by means ofthe constant differential pressure valve 6, a constant relative pressureis maintained within the envelope I. As the balloon rises and theatmospheric pressure decreases the relative pressures within theenvelopes I and 3 tend to increase. Both of these tendencies reflect onthe pressure within envelope 3, and any increase in the relativepressures opens the constant differential pressure valve 0 therebyallowing the escape of air from envelope 3. The increase in the volumeof the gas in envelope I is compensated by the deflation of the envelope3. No gas escapes from envelope I resulting in a constant lifting force.Since all of the expansion of the gas in envelope I is provided for bythe deflation of envelope 3 there is no change in the size or shape ofthe balloon.

Alternatively the non-elastic outer envelope 2 and the elastic innerenvelope I, or gas cell, can

be combined as a single non-elastic envelope made, for example, fromthin sheet plastic material such as polyethylene or polyvinylidenechloride. However, I prefer the two envelope structure because gas-tightelastic envelopes are easier and cheaper to manufacture and have provedmore dependable.

The altitude to which the balloon will ascend depends on the size of theouter envelopes I and 2 and the load that the balloon carries. Thevolume of the outer envelopes must be such as will be completely filledby the amount of gas that is required to lift the load with the desiredlifting force at the proper altitude. After all the air has escaped fromthe inner envelope 3, the relative pressure within the outer envelope Iincreases with a further ascent of the balloon, causing the outerenvelopes to burst.

A balloon to carry 1700 grams to 45,000 feet at 2,850 feet per minutehas the following characteristics: Fineness ratio, 2:1; total volume4,189 cubic feet; volume of hydrogen at sea level and 70 degreesFahrenheit, 524 cubic feet. This amount of hydrogen in a non-elasticballoon provided with outlet means for the hydrogen as it expands wouldcarry the balloon to only 27,000 feet. A hydrogen-filled non-elasticballoon with outlet means for the hydrogen would require 1,839 cubicfeet of hydrogen at sea level to reach 45,000 feet. An elastic ballooncontaining 524 cubic feet of hydrogen would rise at a rate of only about1,800 feet per minute, about the rate of my balloon.

The advantages of my invention are obvious.

My balloon ascends always with the same size and shape, makingstreamlining feasible, and always with a constant lifting force.Balloons having sealed elastic envelopes have a constant lifting force,but do not ascend with a constant size and shape. Ordinary balloons withnon-elastic envelopes maintain the same size and shape, but require acontinual Venting of gas which results in a continually decreasinglifting force and the asymptotic approach to a constant altitude. Myballoon is ideal for operations which require a rapid ascent to theproper altitude whereupon the balloon bursts, as with sounding balloons.

The principle of my invention can also be applied to a high-flying,constant-level balloon by providing a separate differential pressurevalve in communication with the interior of the outer non-elasticenvelope. This valve is adjusted to open when the pressure in thenon-elastic outer envelope increases beyond the pressure required toopen the constant differential pressure valve in communication with theinner envelope. Venting from the outer envelope does not occur until allthe air is vented from the inner envelope. Consequently, after the airfrom the inner envelope is exhausted, a further ascent does not causethe balloon to burst but results in a venting of the lifting gas and acontinual decrease in the ascension velocity to zero when the balloonmaintains a constant altitude. This provides a fast-rising,constant-velocity, constant-level balloon. Higher altitudes are alsorealized for there is no escape of gas until after the balloon reachesthe altitude where the inner air-containing envelope is completelydeflated.

This aspect of my invention is shown in Figure 2. The second constantdifferential pressure valve consists of the tube 20 concentric with thetube 6a, sealed at its outer end by the flange 23, which flange 23 alsosecures the tube 20 to the tube 6a. The upper end of the outer tube 20is in communication with the interior of the outer envelope I. Near thelower end of the tube 28, spaced circumferentially around the lateralperiphery is a number of ports 22, through which gas from the interiorof envelope I can escape. These ports 22 are closed by an elastic band2! placed around the lower end of tube 20 in a manner whereby the ports22 are covered. The tube 24 connects with the interior of the tube 20and provides a means for inflating the outer envelopes I and 2. Thistube 24 is closed with the tapered stopper 24a. The tube 24 and stopper24a in this embodiment of my invention replaces the tube 8 and stopper8a shown in Figure 1.

The differential pressure that this valve will maintain within theenvelope I is controlled by the size and number of ports 22 and by thetension of the elastic band 2|. This diiferential pressure need only besuch as will not burst the outer envelopes I and 2 and can beconveniently preset. Other than allowing the escape of gas from theouter envelope I at such an altitude that all the air in the innerenvelope 3 has been exhausted, this second valve also has the additionalfeature of providing an additional safety valve should the innerenvelope 3 be overinfiated during the inflation of the balloon.

I claim as my invention:

1. A constant-dimension, streamlined, freeflying, self-destructibleballoon comprising an unvented, non-elastic, outer envelope having afineness ratio of about 2:1 adapted to receive a predetermined weight oflifting gas and to retain the gas until the balloon destroys itself andbearing spring extended fins adjacent the tail section adapted tomaintain the balloon in stable vertical flight, an elastic innerenvelope adapted to contain air, and a valve adapted to maintain apredetermined difierential pressure between the air in the innerenvelope and the atmosphere and to permit the escape of air from theinner envelope to the atmosphere whenever the predetermined difierentialpressure in the inner envelope is exceeded and until all the gas fromthe inner envelope is exhausted.

2. A free-flying balloon having a non-elastic outer envelope adapted tocontain gas, a constant differential pressure valve in communicationwith the interior of the outer envelope and venting to the atmosphereadapted to maintain a predetermined differential pressure less than thepressure required to burst the outer envelope between the gas in theouter envelope and the atmosphere and to allow the escape of gas fromthe outer envelope to the atmosphere whenever the predetermined pressuredifierential is exceeded, an elastic inner envelope adapted to containgas, and a second constant differential pressure valve in communicationwith the interior of the inner envelope and venting to the atmosphereadapted to maintain a predetermined differential pressure between thegas in the inner envelope and the atmosphere and to vent gas from theinner envelope to the atmosphere whenever the predetermined pressuredifferential is exceeded and to vent all the gas from the inner envelopebefore the pressure in the outer envelope is great enough to open thefirst named valve.

LANGLEY W. ISOM.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,274,207 Sordyka July 30, 19181,834,614 Hall Dec. 1, 1931 FOREIGN PATENTS Number Country Date 1,318Great Britain of 1892 864,950 France "Feb. 10, 1941

